Manifold vacuum control for power brakes

ABSTRACT

A vehicle having a diesel engine with a fuel supply controlled other than in dependence upon the pressure in the air intake manifold, and a servo assisted braking system the servo unit of which is connected directly to the intake manifold and is activated for application of the brakes by pressure reduction in the intake manifold upon actuation of a choke valve which throttles the air entering the intake manifold. Depression of a brake pedal will close the valve, the depression of an accelerator pedal will force the valve open regardless of the brake pedal position.

United States Patent [1 Neal [ Oct. 9, 1973 MANIFOLD VACUUM CONTROL FOR POWER BRAKES [75] Inventor: Eric R. Neal, Coventry, England [73] l Assignee: Conventry Climax Engines Limited,

Warwickshire, England 22' Filed: May 8,1972

21 Appl. No.: 251,387

[52] US. Cl 192/3 R, 192/3 TR, 123/140 MP,

123/97, 60/14, 188/356 [51] Int. Cl. B601: 29/00 [58] Field of Search 192/3 R, l, 3 TR [56] References Cited UNITED STATES PATENTS 2,949,732 8/ 1960 Schroeder 60/14 1,879,719 9/1932 Stewart t 192/3 R 2,539,994 1/1951 Engler 192/3 R X FOREIGN PATENTS OR APPLICATIONS 292,276 10/1953 Switzerland 192/3 R 308,680 5/1930 Great Britain 192/3 R Primary Examiner-Benjamin W. Wyche Attamey-Joseph F. Brisebois et al.

[57] ABSTRACT A vehicle having a diesel engine with a fuel supply controlled other than in dependence upon thepressure in the air intake manifold, and a servo assisted braking system the servo unit of which is connected directly to the intake manifold and is activated for application of the brakes by pressure reduction in the intake manifold upon actuation of :a choke valve which throttles the air entering the intake manifold. Depression of a brake pedal will close the valve, the depression of an accelerator pedal will force the valve open regardless of the brake pedal position.

1 Claim, 6 Drawing Figures BRAKES It is often required that the braking system of a vehicle be servo-assisted to reduce pedal efforts. Such servo systems are operated by a partial vacuum.

When the vehicle has a petrol engine it is normal practice to use the intake manifold depression to provide the depression required by the servo unit. In the case of diesel engined vehicles, the normal practice is to fit a separate exhaust pump to provide the vacuum necessary to operate the servo unit. The reason for this is that until recent years the fuel injection systems on most vehicle diesel engines have been governed by depression at a venturi in the air intake system, and in such circumstances requirements for fuel supply and brake operation are incompatible. Also the combustion system of the diesel engine is such that maximum intake of air is necessary for efficient working when power is required, irrespective of whether the fuel is controlled by the air intake manifold conditions or not. However in most modern diesel engines the fuel supply is controlled by governers that are divorced from the air intake system.

In accordance with the present invention a vehicle has a diesel engine with a fuel supply controlled other than in dependence upon the pressure in the air intake manifold, and a servo assisted braking system the servo unit of which is connected directly to the intake manifold and is activated for application of the brakes by a depression in the intake manifold upon actuation of a choke valve which throttles the air entering the intake manifold.

With this arrangement no separate exhaust pump is necessary and the required depression for operating the servo unit is created when required in the intake manifold by throttling the air intake.

The choke valve may be a butterfly valve and may be actuated, for example, by movement or loading of the brake foot pedal or linkage, or through a linkage with the accelerator controls.

Three examples of brake servo systems in accor dance with the present invention will now be described with reference to the accompanying drawings, in which:

FIG. I shows a choke valve operated by a vehicle accelerator pedal;

FIG. 2 shows a choke valve operated by a vehicle brake pedal;

FIG. 3 shows the operation of a brake pedal operated choke having an accelerator override; and

FIGS. 3a, 3b and 3c show the operation of the choke of FIG. 3 with the two pedals at different positions.

FIG. 1 shows a vehicle diesel engine 1 having an airintake 2 in which a butterfly valve 3 is positioned. The valve 3 is operated to restrict the air-intake by an accelerator pedal 4, to which the valve is attached by a rigid linkage 5,5. The linkage 5,5 is such that the valve 3 is closed," that is in its maximum throttling position, when the accelerator pedal 4 is in the idle" position, that is when the engine isjust idling. A brake servo unit 6 is connected directly through a conduit 7 into the airintake manifoldbetween the valve 3 and the engine 1. Closure of the valve 3 upon release of the accelerator pedal reduces the pressure by up to 27 inches of mercury on the engine side of the valve and thus provides to the unit 6 the vacuum necessary for the servo operation of the brakes of the vehicle, under the control of a separate brake pedal (not shown).

FIG. 2 shows a system in which a brake pedal 8 is connected via a rigid linkage 9,5 so that depression of the brake pedal 8 to applythe brakes closes the valve 3 thus simultaneously activating the brake servo 6.

In FIG. 3 a system is shown which is similar to that in FIG. 2, but it also has an accelerator override. The rigid brake pedal linkage 9 is attached at one end to the lever 5' which operates the valve 3, and at the other end is attached by a spring connection 10 to the brake pedal 8. The rigid accelerator linkage 5 is attached at one end to the accelerator pedal 4 and at the other end to a slotted link 11 which is slidable on link pin 12 on the lever 5'.

The configuration shown in FIG. 3 is the case in which neither the brake pedal 8 nor accelerator pedal 4 are in use, the valve 3 is therefore open and thus the servo 6 is only activated under a low vacuum.

FIG. 3a shows the footbrake 8 in use, the linkage 9 causing the valve 3 to be closed thereby fully activating the servo. In this case the engine is just idling, the accelerator 4 being unused.

In FIG. 3b the accelerator 4 is in operation, the engine thereby being at speed, and the footbrake 8 is not in use. The valve 3 remains open and there is unrestricted air-flow to the engine.

FIG. 30 shows the accelerator override in operation. The footbrake 8 is in use, but power is required of the engine, for example to drive a subsidiary function such as a load lifting mechanism, and so the accelerator 4 is also in use. The use of the accelerator 4 maintains the valve 3 open or partially open and thus the spring 10 is compressed by movement of the linkage 9. The vacuum applied to the brake servo 6 will be small but still sufficient to hold the vehicle stationary on the footbrake.

I claim:

1. In a vehicle engine having an air intake manifold, a choke valve which throttles the air entering said intake manifold, fuel supply control means independent of the pressure in said air intake manifold, a servo assisted braking system, a brake pedal, and an accelerator control, the improvement according to which a servo unit of said braking system is connected directly to said air intake manifold and activated for application of the brakes by a depression in said intake manifold,

and said brake pedal and accelerator control are connected to said choke valve by linkages such that, while actuation of said brake pedal will close said choke valve to create a depression in said manifold when said accelerator control is in its'idle position, the actuation of said accelerator control will open said choke valve,

regardless of the position of said brake pedal.

- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,7 3,97 Dated 9 October 1973 Patent No.

Inventor( R. It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Foreign Application Priority Data May 12, 1971 Great Britain.. ..1 l 491/7l Signed and sealed this 16th day of April 1971;.

(SEAL) Attest: I

EDWARD I LFLETCHERJR. C. MARSHALL DA'NN Attesting Officer- Commissioner of Patents )RM PO-IOSO (10-69) USCOMM-DC 60876-P59 1i U.S. GOVERNMENT PRINTING OFFICE I," 0566 -33}, 

1. In a vehicle engine having an air intake manifold, a choke valve which throttles the air entering said intake manifold, fuel supply control means independent of the pressure in said air intake manifold, a servo assisted braking system, a brake pedal, and an accelerator control, the improvement according to which a servo unit of said braking system is connected directly to said air intake manifold and activated for application of the brakes by a depression in said intake manifold, and said brake pedal and accelerator control are connected to said choke valve by linkages such that, while actuation of said brake pedal will close said choke valve to create a depression in said manifold when said accelerator control is in its idle position, the actuation of said accelerator control will open said choke valve, regardless of the position of said brake pedal. 